On Mon, Sep 19, 2022 at 4:53 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > Thomas Munro <thomas.mu...@gmail.com> writes: > > On Mon, Sep 19, 2022 at 3:39 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > >> I also note that our existing code in this area would break pretty > >> thoroughly on such a machine, so this isn't making it worse. > > > Yeah, I don't expect it to be a practical problem on any real system > > (that is, I don't expect any real calling convention to transfer a > > struct T * argument in a different place than void *). I just wanted > > to mention that it's a new liberty. > > No, it's not, because the existing coding here is already assuming that. > The walker callbacks are generally declared as taking a "struct *" > second parameter, but expression_tree_walker et al think they are > passing a "void *" to them. Even if a platform ABI had some weird > special rule about how to call functions that you don't know the > argument list for, it wouldn't fix this because the walkers sure do know > what their arguments are. The only reason this code works today is that > in practice, "void *" *is* ABI-compatible with "struct *".
True. > I'm not excited about creating a demonstrable opportunity for bugs > in order to make the code hypothetically more compatible with > hardware designs that are thirty years obsolete. (Hypothetical > in the sense that there's little reason to believe there would > be no other problems.) Fair enough.
